Fluid-jet devices are often used to cut metal parts, fiber-cement siding, stone and many other materials. A typical fluid-jet cutting machine has a high-pressure pump to provide a high-pressure fluid source, and a nozzle is coupled to the high-pressure fluid source to generate a cutting-jet from the nozzle. The nozzle is also attached to a carrier assembly that moves the nozzle along a desired cutting path, and a catch tank is aligned with the nozzle throughout the cutting path. An abrasive particle source may be coupled to the nozzle to impart abrasive particles to the cutting-jet. The fluid is typically water, and the abrasive particles are typically garnet.
In operation of such a fluid-jet cutting machine, a work-piece is positioned between the nozzle and the catch tank. The carrier assembly moves the nozzle along the cutting path, and the high-pressure fluid source and abrasive particle source generate an abrasive cutting-jet projecting from the nozzle. As the cutting-jet passes through the work-piece, the catch tank receives the wastewater and abrasive particles of the spent cutting-jet. The abrasive particles generally accumulate in the catch tank, and the waste water generally flows out of the catch tank.
One concern with fluid-jet cutting systems is that the abrasive particles must be removed from the catch tank. The devices and methods for removing abrasive particles from catch tanks typically depend upon the size of the catch tanks. In general, small catch tanks are typically less than 2'.times.4', and large catch tanks are typically greater than 4'.times.8'.
Conventional techniques for removing abrasive particles from small catch tanks generally allow the wastewater to simply overflow the small catch tanks. Although a portion of the abrasive particles are removed from small catch tanks with the overflowing wastewater, abrasive particles still accumulate in small catch tanks. The remaining abrasive particles are typically removed from small catch tanks by: (1) stopping the cutting-jet to allow the abrasive particles to settle; and (2) shoveling or dumping the abrasive particles from the catch tank.
One problem with conventional techniques from removing abrasive particles from small catch tanks is that the cutting machine must be shut down for a period of time to allow the abrasive particles to settle. Removing abrasive particles from small catch tanks may accordingly result in a significant amount of down-time in a cutting operation. Another problem with removing abrasive particles from small catch tanks is that it is inconvenient and labor intensive to shovel or dump the abrasive particles from the tanks. Therefore, removing abrasive particles from small catch tanks reduces the efficiency and productivity of fluid-jet cutting processes.
Conventional techniques for removing abrasive particles from large catch tanks are different than those for small catch tanks. One conventional abrasive removal system for large catch tanks is a conveyor rake that moves across the bottom of a large catch tank and up a discharge side of the tank. To most effectively operate a conveyor rake, the abrasive particles must settle to the bottom of the tank. The conveyor then carries the abrasive particles from the bottom of the tank and over the discharge side of the tank. One potential problem with conveyor rakes, therefore, is that they may need to be operated when the cutting-jet is shut down causing down-time. Another problem with conveyor rakes is that they may be cut by the cutting-jet during the cutting process if the cutting-jet passes over the portion of the conveyor rake at the discharge side of the catch tank. Additionally, conveyor rake removal systems may be relatively expensive units with many moving components that may fail after extended use. Thus, conveyor rake systems for removing abrasive particles from large catch tanks have several drawbacks.
Another conventional system for removing abrasive particles from large catch tanks is a continuous centrifugal system that has a large pump in the catch tank and a centrifugal separator outside of the catch tank. The large pump agitates the wastewater to suspend the abrasive particles in the catch tank. The wastewater and the suspended abrasive particles are then pumped to a centrifuge, such as a hydrocyclone separator, to separate the abrasive particles from the wastewater. One drawback of this device is that large, expensive pumps are required to maintain the abrasive particles in suspension in the wastewater. Another drawback of this abrasive removal system is that a significant amount of energy is required to operate such large pumps. Additionally, hydrocyclone separators are also relatively costly devices that require additional resources to operate and maintain. Thus, centrifugal removal systems also have several drawbacks.